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W. BARR,J1-., 811 D. MoKAY. METHOD OF FORMING TUBULAR PLAQUBTS OF INDIA RUBBER, M.

Patented May 15,1894.

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5 NA'IIONAL WABHINGTON a c UNITED STATES PATENT OFFICE.

WILLIAM BARR, JR, AND DAVID MCKAY, OF KIRKCUDBRIGHT, SCOTLAND.

METHOD OF FORMING TUBULAR PLAQUETS F INDIA-RUBBER, dic- SEECIFIGATION forming part of Letters Patent No. 519,900, dated May 15, 1894.

Application filed October 31. 1893. Serial No. 489,601. (No specimens.) Patented in England May 31, 1892, No. 10,344: in

, France March 27. 1893. No. 228.923, and in Germany March 30,1893- To aZZwhom it may concern.-

Be it known that we, WILLIAM BARR, Jr., and DAVID MGKAY, subjects of the Queen of Great Britain and Ireland, residing at Kirkcudbright, Kirkcudbrightshire, Scotland,

have invented an Improved Method of Forming Tubular Plaquets and other Tubular Articles of India-Rubber, Ebonite, and the Like, (for which we have obtained Letters Patent in in France, No. 228,923, dated March 27, 1893, and in Germany, dated March 30, 1893,) of which the following is a specification.

Our invention has reference to and comr5 prises an improved method of forming tubular plaquets, and other tubular articles, but specially suitable for forming tubular plaquets of vulcanized dental rubber for use onthe nose frames of eye glasses, also applicable however for forming other tubular articles, especially those of short length,of small diameter and made of dental rubber, ebonite, and the like, and of square, fiat, round, oval, fluted, polygonal and other shapes.

The improvements consist, first, and essentially in the use of brass, copper, German silver, iron, and other wire of smooth surface and suitable temper for a central core, that is, metal which is capable of being annealed until soft enough to stretch without breaking, before being covered with the material which is to form the tubular article, and of being withdrawn by a process of drawing and lengthening said soft metal core in a stretching machine after formation and vulcanization of the tubular article thereon anyhow so that it will become contracted and easily withdrawn from the article, and leave the latter free in its finished state.

In carrying our improved method into practice we use a mold tool formed with a series of U shaped channels in which the plaquet material and central cores are embedded; the product being subsequently vulcanized, and the central cores withdrawn.

In order to enable others skilled in the art to which our invention relates to understand how it may be carried into practice, we have hereunto appended an explanatory sheet of 5 0 drawings in which the same reference letters Great Britain, No. 10,344, dated May 31, 1892;

are used to indicate corresponding parts in all the figures where shown.

Figure 1 is an end elevation partly in section of the mold tool used for forming the tubular articles. Fig. 2 is a plan view of same partly in section, and Fig. 3 is a corresponding edge elevation. Fig. 4 is an end view partly in section of the flask tool used in vulcanizing the tubular articles during their process of manufacture. Fig. 5 is a plan view of one of the upper frames, and Fig. 6 a corresponding view of the base plate; while Fig. 7 is a corresponding edge elevation of this tool. Figs. 8 and 9 are an inverted plan view, and end section showing three tubular plaquet articles with their metal cores as formed in one piece after coming out of the tool shown in Figs. 1 to 3; and Figs. 10 and 11 are a plan view and end section respectively of a tubular plaquct article complete after vulcanization and removal of the internal metal core.

Referring to the drawingsz-The tool shown in Figs. 1 to 3 consists of a base plate A formed with a series of longitudinal vertical ribs a with U shaped channels a between these and a series of vertical projections a at the two ends of these vertical ribs a the base plate A being covered over with a top plate A with center wings A after the wires and sheets of rubber have been inserted.

The tool shown in Figs. 4 to 7 consists of four movable parts a lower and upper plate B and B and two intermediate rectangular open frames B B the upper of these B shown detached in Fig. 5, being formed with a series of notched grooves 12 to receive the ends of the metal cores in the tubular plaquets.

To manufacture thetubular plaqnets we proceed as follows:-Taking the tool shown in-Figs. l to 3 having a series of U shaped channels a we dust it over with French chalk carefully blowing out all that may be lying loose; we do the same with the inside of the lid. \Ve then lay a sheet of dental rubber over channels a Over this, and. in each channel, we place one of our annealed metal cores 0, and, over these again, a sheet of dental rubber. Taking lid A we place it on, and then apply pressure such pressure as too is obtainable from an ordinary letter press or got our plaquets molded into shape) they formed under pressure.

are ready for vulcanizing. This is done in exactly the same way as dentists vulcanize their work, namely, as surrounded with plaster of paris in molds and under pressure. Our practice may be best explained by the tool formed of four brass pieces, shown in Figs. 4 to 7.. These brass pieces when put together, as shown in Fig. 4 constitutea flask. They are made up of two lids, and two rectangular open frames B B just under one-fourth of an inch deep. Into this flask we put our sheet of unvulcanized plaquets surrounded with plaster of paris. Before the plaster of paris sets they are subjected to pressure in an ordinary cramp and allowed to harden before vulcanization. Vulcanization must be per- When more than one flask containing p'laquets are to be vulcanized they may be placed on top of each other in a cramp sufticiently large to include them all and keep all under pressure.

We fill our flasks with plaster of paris and unvulcanized plaquets as follows:The process is simple. Taking a flat marble slab, about a foot square, place the halt of flask thereon (half of flask consists of one of the lids B B and one of the rectangular squares B B Into this poura mixture of plaster of paris and water, such mixture to be as thick as say good cream, and beforeit has had time to set, also place in the flask, face downward and in plaster of paris the sheet of p'laquets to be vulcanized taking good care to work the same backward and forward in the plaster of now put on and the cramp (as described for applying pressure to single flasks of plaquets) brought into use. Flasks thus pressed and allowed to harden or set may lie aslde until other similar flasks are ready, when all may be vulcanized together in an exactly similar cramp but large enough to contain them. It will be seen from what we have described, that the plaquets to be vulcanized are in the center of their plaster of paris surroundings.

Plaquets being cut up into'length-s having a central wire or core in each, the free ends of said soft metallic central cores are placed in a wire stretching machine, and after stretching the cores a little they can be read ily Withdrawn, so leaving the tubular plaquet articles free as seen in Figs. 10 and 11.

What we claim is A method of forming tubular plaquets and other tubular articles of dental rubber, ebon ite and the like, consisting in surrounding an annealed metal core with the dental rubber or the like, then vulcanizing the rubber, and stretching the said annealed core whereby the core is contracted in diameter, and then withdrawing the core, substantially as and for the purpose set forth.

In testimony whereof we have signed our names to this specification in the presence of two subscribing witnesses.

WILLIAM BARR, JUNR. DAVID MGKAY. Witnesses:

JAMES PALMER, SAMUEL J. LITTLE. 

